This invention generally relates to diagnostic systems, and more particularly to a battery energy management system for measuring a minimum battery voltage and an elapsed time of the minimum battery voltage.
Electrical systems, such as automotive electrical systems, are becoming increasingly complex. Known electrical systems typically include a microcontroller which controls the operation of a variety of electrical systems found thereon, including but not limited to remote keyless entry systems, passive entry and starting systems, tire pressure monitoring systems and vehicle diagnostic systems. Other known devices, such as cell phones and medical devices, also utilize a microcontroller which controls the electrical systems within these devices. The microcontrollers of many of these systems may be overloaded because of the numerous electrical systems for which the microcontroller must control and operate.
One function of vehicle diagnostic systems includes detecting and measuring a minimum battery voltage of a vehicle battery when starting a vehicle (i.e., during engine cranking). The minimum battery voltage of a vehicle battery is measured to ensure that the energy level of the battery is sufficient to supply an adequate amount of power to the numerous electrical systems of the vehicle such that these systems operate properly. The vehicle diagnostic system measures the minimum battery voltage and alerts the vehicle operator by communicating a battery error signal to the operator where the detected minimum battery voltage is below a certain level, for example.
One known vehicle diagnostic system includes a battery energy management system which is entirely implemented with the internal peripherals of the microcontroller. The microcontroller utilizes an analog to digital (A/D) converter and internal timer peripherals to measure the minimum battery voltage. Disadvantageously, the microcontroller loading requirements are increased by the necessity to detect and measure the minimum battery voltage. The increase in microcontroller load, when combined with the resources already expended by the microcontroller to control the various other electrical systems of the vehicle, may result in less accurate minimum battery voltage measurements and delayed functionality of the remaining electrical systems of the vehicle. Similar problems may be experienced by the microcontrollers of other devices (i.e. cell phones, medical devices, etc.).
Accordingly, it is desirable to provide a battery energy management system that detects and measures a minimum battery voltage and an elapsed time of the minimum battery voltage while simultaneously reducing the load requirements of a system microcontroller.